Cross-protection induced by cross-reactive antigen against Fasciola gigantica and Trichinella spiralis infections.

Trichinella spiralis /Fasciola gigantica cross-reactive fraction was purified from T. spiralis larval extract by affinity column chromatography in which CNBr-Sepharose 4B was coupled with F. gigantica antibodies. The fraction consisted of six polypeptides of 191KDa, 178KDa, 149KDa, 106KDa, 101KDa and 32 KDa as revealed by SDS-PAGE. Analysis of the free amino acids of the fraction revealed 17 amino acids with high proportions of tyrosine and glutamic. Immunization of rabbits subcutaneously with the cross-reactive fraction in Freund's adjuvant followed by challenge with F. gigantica metacercariae resulted in reduction in worm burdens reached to 47.8%. While immunization of rats with the same fraction in Freund's adjuvant followed by infection with T. spiralis larvae resulted in reduction in worm count reached to 74%. IgG antibody response in rabbits increased due to immunization to reach its maximum value at the time of infection and then decreased gradually up to the end of the experiments. But. remained higher than the level in non vaccinated control animals. In rat sera, IgG level increased due to vaccination but the level recorded its optimum value one week post infection and then decreased. Thus the cross-reactive antigen proved cross-protection with the protection inducing capability against both diseases.